The following was originally proposed for KGSWishlist, but it could be used anywhere on SL:
If you like an idea, mark it with "[+|YourName]", if you don't with "[-|YourName]". This results in +++ marks following an entry agreed with 3 times, hovering over each plus sign will show you who gave each mark.
Instead of using YourName, you may consider using YourName/Votes, and put a text like the one on Sebastian/Votes there. This has the following advantages: